This invention relates to compositions that are useful as ink jet recording media topcoats, recording media for ink jet images, processes for making ink jet recording media, processes for recording images on ink jet recording media, and images made by such processes.
Ink jet printers are a well known means for creating black and white or color images on a recording medium. The images are created by generating small droplets of ink which are propelled onto the recording medium. The ink generally contains a water-based dye or dispersed pigment and the recording medium is often paper, but may also be a coated polymeric film as in the case of transparencies for overhead projectors. Advantages with this type of printing include the ability to create high resolution full color images rapidly and in large formats using digitally generated and stored images. Furthermore, it is quiet and environmentally friendly and safe.
Ink jet printing is frequently used to produce graphics for outdoor applications. These outdoor applications require both the inks and the recording medium to be resistant to water, sunlight and extremes in temperature without sacrificing image quality. Recent advances in outdoor recording media include the use of water-insoluble polyamide topcoats to improve UV and water resistance of the recording medium.
However, the use of a topcoat tends to cause tension in the recording media which may result in the media curling. Additionally, the strength of the commercially available topcoats is limited by the internal bond strength of the coating. Likewise, improved abrasion resistance and color density are other desired characteristics of new ink jet media coatings. The present invention addresses these and other problems associated with prior art topcoat formulations.
In one embodiment, the invention is a coating composition for ink jet recording media, the coating composition comprising:
(a) At least one non-ionic surfactant;
(b) At least one dispersing agent;
(c) At least one ionomer;
(d) At least one polyamide binder, the polyamide binder having a surface energy of at least about 40 dyne/cm as measured by ASTM D2578-94; and
(e) At least one particulate filler.
Yet another embodiment of this invention is a substrate coated with the inventive composition. A further embodiment is a method for increasing the weather resistance of ink-jet recorded images, the method comprising the steps of (i) applying the coating composition to a support material, and (ii) curing the coating material on the support material. Other embodiments are similar methods for increasing resistance to dry abrasion, increasing resistance to wet abrasion, increasing resistance to curl, and decreasing color density loss upon immersion in water.
The invention involves the use of ionomers, dispersing agents, and surfactants to produce ink jet coatings with hallmarks including, inter alia, superior resistance to water, high internal bond strength, scratch resistance, reduced tendency to curl, and increased color density.